To grab a reader, your story needs to be moving at the right speed—not slowed down by unnecessary words or dead spaces.  Always start it in medias res (in the middle of things), which means at the first moment the story actually begins (with no leading-up-to, introduction, or backstory).  The purpose of a first line is to get the reader to Line 2.  Hunter Thompson’s, in Fear and Loathing in Las Vegas, is a great one: “We were somewhere around Barstow on the edge of the desert when the drugs began to take hold.”  Ken Follett’s “The last camel collapsed at noon,” which opens The Key to Rebecca, is also splendid.  What reader could fail to read Line 2 of either book?  The purpose of the second line is to get the reader to the bottom of the page.  Once you get them there and they flip the page, they’re yours to lose.